Motor vehicle bumper

ABSTRACT

A motor vehicle bumper system comprising an outer shell ( 10 ) of an automotive bumper having an inner surface ( 18 ) generally oriented toward the vehicle. The outer shell comprises a plurality of energy absorbing protuberances ( 14 ) extending inwardly from the inner surface of the outer shell. The energy absorbing protuberances may be formed from an energy absorbing material, such as a polymeric foam, and/or may additionally comprise indentations extending into the body of the protuberance to enhance the energy absorbing characteristics of the protuberance.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the National Stage of International Application No.PCT/US01/17433 filed May 31, 2001 and published Dec. 6, 2001 asInternational Publication No. WO 01/92064, designating the UnitedStates, and which claims benefit of U.S. Provisional Application No.60/208,146 filed May 31, 2000.

This invention relates generally to motor vehicle bumper systems, andmore particularly, to bumper systems comprising a fascia with integralenergy absorbers.

In automotive applications bumpers ore employed not only to control andlimit the energy from an impact as it enters the vehicle, typicallychanneling the energy into structural members of the vehicle, but alsoto limit the damage to a vehicle as a result of relatively minoraccidents, thereby fulfilling the 5 mph impact test. In the pastautomotive bumpers came in two general varieties.

A first general variety of known bumpers comprises an outer fasciahaving a layer of energy absorbing foam, typically a polyurethane foam,disposed behind the fascia. The fascia and foam are further attached toa structural bumper beam. According to this first variety of bumperassembly, the fascia provides the cosmetic outer surface viewable fromthe exterior of the vehicle. Under an impact event, impact energy to thefascia is, to some degree, absorbed or dissipated by the energyabsorbing foam material. The bumper beam is designed to absorb theimpact and route it to structural components of the vehicle, such asframe rails.

The second general variety of bumper assemblies comprises a fascia, abumper beam and, usually two, hydraulic or pneumatic piston type shockabsorbers. According to this variety of bumper, as with the firstvariety, the fascia fulfills the aesthetic requirements of the bumperassembly. The bumper beam is typically a metallic member disposedbehind, and/or contained within the fascia, for receiving the energy ofan impact and channeling the energy to the shock absorbers. The shockabsorbers, as with the shocks in the suspension system, absorb andlessen the energy of an impact and transfer the remainder of the energyto structural components of the vehicle, such as frame rails.

The present invention is an automotive bumper system comprising a anouter shell having at least one, but preferably several, energyabsorbing features disposed adjacent thereto. The energy absorbingfeatures preferable functionally comprise projections from an innersurface of the outer shell. These energy absorbing features may actuallybe integral with the inner surface of the outer shell, or may beseparate components disposed adjacent to the inner surface of the outershell. The energy absorbing features may include cones, pyramids,cylinders, or truncated variations of the previous. Additionally, theenergy absorbing characteristics of the energy absorbers may be modifiedby providing them with indentations. The energy absorbers and the outershell both preferably comprise a polymeric material, although notnecessarily the same polymeric material.

Further, the present invention provides a method of making a bumperhaving energy absorbing features. Preferably the method is a sequentialmolding operation wherein the outer shell is formed of a polymericmaterial in a first mold. Subsequently the energy absorbing features areformed integrally with the inner surface of the outer shell using a moldwherein at least a portion of the mold is defined by the previouslyformed outer shell inner surface. Alternately, the energy absorbingfeatures maybe formed first, and the outer shell formed subsequentlythereto. Consistent with this last, as least a portion of the moldforming the inner surface of the outer shell is defined by at least aportion of the previously formed energy absorbers.

In an alternate method of forming the bumper system, the outer shell isformed separately from the energy absorbers. The separately formed outershell and energy absorbers may subsequently be joined together bymethods including thermal bonding, adhesive bonding, solvent welding,mechanical fastening etc.

To better understand and appreciate the invention, refer to thefollowing detailed description in connection the accompanying drawings:

FIG. 1 is a rear perspective view of a fascia with the fascia partiallycut away to show a pattern of energy absorbers; and

FIG. 2 is a cross sectional view of the fascia of FIG. 1 taken alongline 2—2.

An exemplary outer shell is shown generally at 10 in FIG. 1. As shown,outer shell 10 is a fascia of a motor-vehicle. As shown in FIG. 2, theouter shell 10 is generally the aesthetic component of a bumper system12, and covers the internal components of the bumper system 12 includingan energy absorber 14 and support structure 16, such as a bumper beam.

Outer shell 10 has an inner surface 18 and an outer surface 20, andcomprises a plastic material. At least one, and more preferably aplurality of, energy absorbers 14 are attached to outer shell 10. Theenergy absorbers 14 comprise isolated protuberances projecting from theinner surface 18 of the outer shell 10. Preferred designs of the energyabsorbers 14 comprise cylinders, cones, truncated cones, pyramids, ortruncated pyramids.

As shown in FIG. 2, energy absorbers 14 are disposed adjacent thesupport structure 16 when outer shell 10 is assembled to the vehicle. Inthe case of an impact to the outer surface 20 of outer shell 10, energyabsorbers 14 deform and absorb either the entire impact energy or atleast a portion thereof. Optionally, and depending on the magnitude ofthe impact, the energy absorbers 14 may also transmit energy to thesupport structure 16.

The energy absorption characteristics of energy absorbers 14 may bemodified by providing the energy absorbers 14 with at least oneindentation 22, preferably extending from a surface adjacent the supportstructure towards the inner surface 18 of the outer shell 10, thereinproviding the energy absorbers 14 with a cored construction.

The energy absorbing characteristics of energy absorbers 14 may furtherbe modified by varying the number of, and separation between, energyabsorbers 14. Thus, for example, in response to an impact of greaterenergy, the number of energy absorbers may be increased. It can furtherbe appreciated that the height of energy absorber 14 (i.e. the distancebetween the surface adjacent the support structure and the inner surface18 of the outer shell 10), as well as the ratio of cross-sectional areaof the surface of energy absorber 14 in contact with inner surface 18will also alter the energy absorbing characteristics. The energyabsorbing characteristics of the energy absorbers 14 may be furthermodified by connecting the energy absorbers with a rib 24 structure toform an egg crate or grid structure.

Outer shell 10 is preferably formed from a thermoplastic material usinga thermoplastic injection molding process. An exemplary thermoplasticmaterial comprises polypropylene (PP). However, outer shell 10 may alsobe formed from a thermoset material using, for example, a reactioninjection molding process. An exemplary thermoset material comprisesthermoset polyurethane. Other foxing techniques may include, but are notlimited to, injection-compression molding, compression molding,thermoforming, vacuum forming, pressure forming and blow molding. It ispreferred that the outer shell 10 be molded in color, thereby obviatingthe need for post process painting or finishing.

Energy absorbers 14 are preferably formed from an energy absorbingpolymer material, more preferably an expanded polymeric foam material.The energy absorbing foam material may comprise a thermoplastic orthermoset polymeric material, and the blowing agent used to foam thepolymer may be chemical or physical. Alternately, as noted, energyabsorbers 14 may be formed from a solid thermoplastic or thermosetpolymeric material. An exemplary thermoplastic material comprisespolypropylene (PP), while an exemplary thermoset material comprisesthermoset polyurethane. In the case of thermoplastic material, energyabsorbers 14 are preferably formed by injection molding. In the case ofthermoset materials, energy absorbers 14 are preferably formed byreaction injection molding.

Preferably, outer shell 10 and energy absorbers 14 are manufacturedusing a sequential two-step molding process. When outer shell 10 andenergy absorbers 14 are formed using a sequential two-step moldingprocess, energy absorber 14 are formed from a first polymeric materialinjected or otherwise introduced, into a first mold cavity comprisingthe shape of energy absorbers 14. The mold is then adjusted to provide asecond mold cavity comprising the shape of the outer shell 10. Outershell 10 is then formed from a second polymeric material injected intothe second mold cavity. Preferably, the inner surface 18 of outer shell10 bonds to energy absorbers 14 during the molding operation.Alternately, outer shell 10 maybe formed first, and the energy absorbers14 maybe formed thereafter.

When a sequential molding process is utilized, it is further preferredthat a rotatable, or turntable, platen molding apparatus be employed. Asresult, the outer shell 10 and energy absorbers 14 may be molded using asingle, integrated piece of equipment, rather than having to transferthe first molded object to a second piece of molding equipment. When arotatable platen molding apparatus is used, the first mold cavitycomprising the shape of the energy absorbers 14 starts the molding cycleat a first molding station. At the first molding station, polymericmaterial is introduced into a mold comprising the first mold cavity.Shortly thereafter, the rotatable platen is rotated approximately 120degrees and the molded energy absorbers 14 are indexed to a secondmolding station. At the second molding station, polymeric material isintroduced into a mold comprising the second mold cavity comprising theouter shell 10. Preferably, the inner surface 18 of outer shell 10 bondsto the energy absorber 14 during or shortly after molding. Shortlythereafter, the rotatable platen is rotated approximately 120 degreesand the formed energy absorbers 14 and outer shell 10 are indexed to ade-mold station where they are removed from the molding operation.Alternately, and again as noted above, the outer shell 10 may be formedin the first mold cavity and the energy absorber 14 maybe formed in thesecond mold cavity.

Alternately, the outer shell 10 and energy absorbers 14 may be formed incompletely separate independent mold operations and, rather than beingjoined during the formation of the second piece, may be joinedsubsequently after both pieces are first formed. When outer shell 10 andenergy absorbers 14 are separately molded, preferred methods of joininginclude, but are not limited to, thermal welding, thermal bonding,solvent bonding, mechanical attachment and/or adhesive bonding, as wellas combinations thereof.

Alternatively, outer shell 10 and energy absorbers 14 maybe formed atthe same time and from the same polymeric material. This will reduce thenumber of mold cavities required from two to one, and reduce thecomplexity of the equipment and the molding operation.

As can therefore be seen from the above, various modifications can beapplied to the invention herein, without departing from the broad scopeof a bumper system containing energy absorbing capabilities.

1. An automotive bumper comprising an outer shell having an innersurface and at least one energy absorber, said at least one energyabsorber comprising a protuberance disposed adjacent to and projectingfrom said inner surface of said outer shell, wherein said protuberanceis integral with the inner surface of the outer shell.
 2. The automotivebumper according to claim 1 wherein said at least one energy absorbercomprises at least one indentation extending generally from an energyabsorber surface distal said outer shell toward said outer shell.
 3. Theautomotive bumper according to claim 1 comprising a plurality of energyabsorbers wherein said plurality of energy absorbers are connected by atleast one rib.
 4. A method of producing an automotive bumper comprising:forming a bumper outer shell having an inner surface; forming at leastone energy absorber comprising a protuberance; joining said at least oneenergy absorber to said inner surface of said outer shell such that saidat least one energy absorber extends from said inner surface of saidouter shell, wherein said protuberance is integral with the innersurface of the outer shell.
 5. A method of producing an automotivebumper comprising: providing a mold cavity defining an outer shellhaving an inner surface said inner surface having at least one energyabsorber projecting therefrom, wherein said protuberance is integralwith the inner surface of the outer shell; introducing a polymericmaterial into said mold cavity; and at least partially solidifying saidpolymeric material.
 6. A method of producing an automotive bumpercomprising; providing a first mold cavity defining an outer shell havingan inner surface; introducing a first polymeric material into said firstmold cavity; at least partially solidifying said first polymericmaterial; adjusting said first mold cavity to provide a second moldcavity defining at least one energy absorber, said at least one energyabsorber at least partially defined by said at least partiallysolidified inner surface of said outer shell; introducing a secondpolymeric material into said second mold cavity; and at least partiallysolidifying said second polymeric material.
 7. The method according toclaim 6 wherein the step of adjusting said first mold cavity to providea second mold cavity comprises rotating a portion of said first moldcavity and indexing said portion of said first mold cavity with saidsecond mold cavity.
 8. A method of producing an automotive bumpercomprising; providing a first mold cavity defining at least one energyabsorber; introducing a first polymeric material into said first moldcavity; at least partially solidifying said first polymeric material;adjusting said first mold cavity to provide a second mold cavitydefining an outer shell having an inner surface, wherein at least aportion of said inner surface of said outer shell is defined by at leasta portion of said at least one energy absorber; introducing a secondpolymeric material into said second mold cavity; and at least partiallysolidifying said second polymeric material.
 9. The method according toclaim 8 wherein the step of adjusting said first mold cavity to providea second mold cavity comprises rotating a portion of said first moldcavity and indexing said portion of said first mold cavity with saidsecond mold cavity.